From: "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: Jeff Hostetler <git@jeffhostetler.com>,
Johannes Schindelin <johannes.schindelin@gmx.de>,
Johannes Schindelin <johannes.schindelin@gmx.de>
Subject: [PATCH 2/4] split-index; stop abusing the `base_oid` to strip the "link" extension
Date: Wed, 22 Mar 2023 16:00:57 +0000 [thread overview]
Message-ID: <f1897b880729b649ab24da14cbc3432d44b7c731.1679500859.git.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.1497.git.1679500859.gitgitgadget@gmail.com>
From: Johannes Schindelin <johannes.schindelin@gmx.de>
When a split-index is in effect, the `$GIT_DIR/index` file needs to
contain a "link" extension that contains all the information about the
split-index, including the information about the shared index.
However, in some cases Git needs to suppress writing that "link"
extension (i.e. to fall back to writing a full index) even if the
in-memory index structure _has_ a `split_index` configured. This is the
case e.g. when "too many not shared" index entries exist.
In such instances, the current code sets the `base_oid` field of said
`split_index` structure to all-zero to indicate that `do_write_index()`
should skip writing the "link" extension.
This can lead to problems later on, when the in-memory index is still
used to perform other operations and eventually wants to write a
split-index, detects the presence of the `split_index` and reuses that,
too (under the assumption that it has been initialized correctly and
still has a non-null `base_oid`).
Let's stop zeroing out the `base_oid` to indicate that the "link"
extension should not be written.
One might be tempted to simply call `discard_split_index()` instead,
under the assumption that Git decided to write a non-split index and
therefore the the `split_index` structure might no longer be wanted.
However, that is not possible because that would release index entries
in `split_index->base` that are likely to still be in use. Therefore we
cannot do that.
The next best thing we _can_ do is to introduce a flag, specifically
indicating when the "link" extension should be skipped. So that's what
we do here.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
read-cache.c | 37 ++++++++++++++++++++++--------------
t/t7527-builtin-fsmonitor.sh | 2 +-
2 files changed, 24 insertions(+), 15 deletions(-)
diff --git a/read-cache.c b/read-cache.c
index b09128b1884..8fcb2d54c05 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -2868,6 +2868,12 @@ static int record_ieot(void)
return !git_config_get_index_threads(&val) && val != 1;
}
+enum strip_extensions {
+ WRITE_ALL_EXTENSIONS = 0,
+ STRIP_ALL_EXTENSIONS = 1,
+ STRIP_LINK_EXTENSION_ONLY = 2
+};
+
/*
* On success, `tempfile` is closed. If it is the temporary file
* of a `struct lock_file`, we will therefore effectively perform
@@ -2876,7 +2882,7 @@ static int record_ieot(void)
* rely on it.
*/
static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
- int strip_extensions, unsigned flags)
+ enum strip_extensions strip_extensions, unsigned flags)
{
uint64_t start = getnanotime();
struct hashfile *f;
@@ -3045,7 +3051,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
return -1;
}
- if (!strip_extensions && istate->split_index &&
+ if (strip_extensions == WRITE_ALL_EXTENSIONS && istate->split_index &&
!is_null_oid(&istate->split_index->base_oid)) {
struct strbuf sb = STRBUF_INIT;
@@ -3060,7 +3066,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
if (err)
return -1;
}
- if (!strip_extensions && !drop_cache_tree && istate->cache_tree) {
+ if (strip_extensions != STRIP_ALL_EXTENSIONS && !drop_cache_tree && istate->cache_tree) {
struct strbuf sb = STRBUF_INIT;
cache_tree_write(&sb, istate->cache_tree);
@@ -3070,7 +3076,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
if (err)
return -1;
}
- if (!strip_extensions && istate->resolve_undo) {
+ if (strip_extensions != STRIP_ALL_EXTENSIONS && istate->resolve_undo) {
struct strbuf sb = STRBUF_INIT;
resolve_undo_write(&sb, istate->resolve_undo);
@@ -3081,7 +3087,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
if (err)
return -1;
}
- if (!strip_extensions && istate->untracked) {
+ if (strip_extensions != STRIP_ALL_EXTENSIONS && istate->untracked) {
struct strbuf sb = STRBUF_INIT;
write_untracked_extension(&sb, istate->untracked);
@@ -3092,7 +3098,7 @@ static int do_write_index(struct index_state *istate, struct tempfile *tempfile,
if (err)
return -1;
}
- if (!strip_extensions && istate->fsmonitor_last_update) {
+ if (strip_extensions != STRIP_ALL_EXTENSIONS && istate->fsmonitor_last_update) {
struct strbuf sb = STRBUF_INIT;
write_fsmonitor_extension(&sb, istate);
@@ -3166,8 +3172,14 @@ static int commit_locked_index(struct lock_file *lk)
return commit_lock_file(lk);
}
+/*
+ * Write the Git index into a `.lock` file
+ *
+ * If `strip_link_extension` is non-zero, avoid writing any "link" extension
+ * (used by the split-index feature).
+ */
static int do_write_locked_index(struct index_state *istate, struct lock_file *lock,
- unsigned flags)
+ unsigned flags, int strip_link_extension)
{
int ret;
int was_full = istate->sparse_index == INDEX_EXPANDED;
@@ -3185,7 +3197,7 @@ static int do_write_locked_index(struct index_state *istate, struct lock_file *l
*/
trace2_region_enter_printf("index", "do_write_index", the_repository,
"%s", get_lock_file_path(lock));
- ret = do_write_index(istate, lock->tempfile, 0, flags);
+ ret = do_write_index(istate, lock->tempfile, strip_link_extension ? STRIP_LINK_EXTENSION_ONLY : 0, flags);
trace2_region_leave_printf("index", "do_write_index", the_repository,
"%s", get_lock_file_path(lock));
@@ -3214,7 +3226,7 @@ static int write_split_index(struct index_state *istate,
{
int ret;
prepare_to_write_split_index(istate);
- ret = do_write_locked_index(istate, lock, flags);
+ ret = do_write_locked_index(istate, lock, flags, 0);
finish_writing_split_index(istate);
return ret;
}
@@ -3366,9 +3378,7 @@ int write_locked_index(struct index_state *istate, struct lock_file *lock,
if ((!si && !test_split_index_env) ||
alternate_index_output ||
(istate->cache_changed & ~EXTMASK)) {
- if (si)
- oidclr(&si->base_oid);
- ret = do_write_locked_index(istate, lock, flags);
+ ret = do_write_locked_index(istate, lock, flags, 1);
goto out;
}
@@ -3394,8 +3404,7 @@ int write_locked_index(struct index_state *istate, struct lock_file *lock,
/* Same initial permissions as the main .git/index file */
temp = mks_tempfile_sm(git_path("sharedindex_XXXXXX"), 0, 0666);
if (!temp) {
- oidclr(&si->base_oid);
- ret = do_write_locked_index(istate, lock, flags);
+ ret = do_write_locked_index(istate, lock, flags, 1);
goto out;
}
ret = write_shared_index(istate, &temp, flags);
diff --git a/t/t7527-builtin-fsmonitor.sh b/t/t7527-builtin-fsmonitor.sh
index cbafdd69602..9fab9a2ab38 100755
--- a/t/t7527-builtin-fsmonitor.sh
+++ b/t/t7527-builtin-fsmonitor.sh
@@ -1003,7 +1003,7 @@ test_expect_success !UNICODE_COMPOSITION_SENSITIVE 'Unicode nfc/nfd' '
egrep "^event: nfd/d_${utf8_nfc}/?$" ./unicode.trace
'
-test_expect_failure 'split-index and FSMonitor work well together' '
+test_expect_success 'split-index and FSMonitor work well together' '
git init split-index &&
test_when_finished "git -C \"$PWD/split-index\" \
fsmonitor--daemon stop" &&
--
gitgitgadget
next prev parent reply other threads:[~2023-03-22 16:01 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-22 16:00 [PATCH 0/4] Fix a few split-index bugs Johannes Schindelin via GitGitGadget
2023-03-22 16:00 ` [PATCH 1/4] split-index & fsmonitor: demonstrate a bug Johannes Schindelin via GitGitGadget
2023-03-23 13:39 ` Jeff Hostetler
2023-03-22 16:00 ` Johannes Schindelin via GitGitGadget [this message]
2023-03-22 21:24 ` [PATCH 2/4] split-index; stop abusing the `base_oid` to strip the "link" extension Junio C Hamano
2023-03-23 13:59 ` Jeff Hostetler
2023-03-23 16:06 ` Junio C Hamano
2023-03-23 15:22 ` Jeff Hostetler
2023-03-22 16:00 ` [PATCH 3/4] fsmonitor: avoid overriding `cache_changed` bits Johannes Schindelin via GitGitGadget
2023-03-22 16:00 ` [PATCH 4/4] unpack-trees: take care to propagate the split-index flag Johannes Schindelin via GitGitGadget
2023-03-23 14:32 ` Jeff Hostetler
2023-03-22 16:22 ` [PATCH 0/4] Fix a few split-index bugs Junio C Hamano
2023-03-26 22:45 ` [PATCH v2 " Johannes Schindelin via GitGitGadget
2023-03-26 22:45 ` [PATCH v2 1/4] split-index & fsmonitor: demonstrate a bug Johannes Schindelin via GitGitGadget
2023-03-26 22:45 ` [PATCH v2 2/4] split-index; stop abusing the `base_oid` to strip the "link" extension Johannes Schindelin via GitGitGadget
2023-03-26 22:45 ` [PATCH v2 3/4] fsmonitor: avoid overriding `cache_changed` bits Johannes Schindelin via GitGitGadget
2023-03-26 22:45 ` [PATCH v2 4/4] unpack-trees: take care to propagate the split-index flag Johannes Schindelin via GitGitGadget
2023-03-27 14:48 ` [PATCH v2 0/4] Fix a few split-index bugs Jeff Hostetler
2023-03-27 16:42 ` Junio C Hamano
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=f1897b880729b649ab24da14cbc3432d44b7c731.1679500859.git.gitgitgadget@gmail.com \
--to=gitgitgadget@gmail.com \
--cc=git@jeffhostetler.com \
--cc=git@vger.kernel.org \
--cc=johannes.schindelin@gmx.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).